Low profile dental impression tray and set of such trays

ABSTRACT

A set of dental impression trays for both mixed and permanent dentition is provided wherein the members of the set differ primarily in the size of the dental arch and lateral distance between corresponding molar positions on opposite sides of the jaw. A rise is provided in the retromolar and tuberosity areas of the permanent dentition. Each tray in the set is a rigid low profile member comprised of a narrow substantially planar Ushaped base, lingual and labial walls integral with the base and upstanding from opposite edges thereof to provide a generally Ushaped cross section, an anterior handle projecting outwardly from the base and the labial wall and lateral tabs on opposite sides of the anterior handle extending laterally outwardly from the base at an acute angle thereto, said lateral tabs being located at the bicuspid/molar region on opposite sides of the tray. The base of each tray within the set has the same transverse dimension in respective locations of the tray.

United States Patent 11 1 Coscina [451 Apr. 22, 1975 LOW PROFILE DENTAL IMPRESSION TRAY AND SET OF SUCH TRAYS [76] Inventor: William Alfred Coscina, 41

Westwood Dr., New Britain, Conn. 06052 [22] Filed: Nov. 19, 1973 [21] Appl. No.: 417,102

Primary E.\'aminerRobert Peshock Attorney, Agent, or Firm-Prutzman, Hayes, Kalb & Chilton [57] ABSTRACT A set of dental impression trays for both mixed and permanent dentition is provided wherein the members of the set differ primarily in the size of the dental arch and lateral distance between corresponding molar positions on opposite sides of the jaw. A rise is provided in the retromolar and tuberosity areas of the permanent dentition. Each tray in the set is a rigid low profile member comprised of a narrow substantially planar U-shaped base, lingual and labial walls integral with the base and upstanding from opposite edges thereof to provide a generally U-shaped cross section. an anterior handle projecting outwardly from the base and the labial wall and lateral tabs on opposite sides of the anterior handle extending laterally outwardly from the base at an acute angle thereto, said lateral tabs being located at the bicuspid/molar region on opposite sides of the tray. The base of each tray within the set has the same transverse dimension in respective locations of the tray.

12 Claims, 9 Drawing Figures LOW PROFILE DENTAL IMPRESSION TRAY AND SET OF SUCH TRAYS BACKGROUND AND SUMMARY OF THE IN- VENTION The present invention relates generally to dental impression trays. More specifically it is concerned with a new and improved low profile impression tray particularly well suited for crown and bridgework and to a set of such trays.

It has been well established that the use of full models of a patients dentition and its surrounding soft periodontal tissue provides the most accurate method of obtaining models for use in crown and bridgework. However, impression trays utilized heretofore to produce such full models for registration of the dentition have been relatively large and bulky and have encompassed an excessive amount of supporting soft tissue not truly necessary for the desired registration of the dentition and soft tissue structure. Such bulky structures require the use of inordinate amounts of expensive impression material and frequently result in not only unnecessary discomfort to the patient while the impression is being taken but also gagging of the patient and irritation of the patients cheeks, mouth floor and palate. Additionally, when the impression tray is used with wash-type impression material and, it is necessary to reinsert the tray, it has been found that distortions frequently occur in the impression and that marginal registration is inaccurately taken due to the bulky nature of the tray and particularly due to the fact that the dentist is limited to the use of a single handle for the purposes of positioning and manipulating the tray.

In some existing impression tray structures, the tray is provided with a smooth interior surface and the impression material is secured thereto by the use of the adhesive. However, it has been found that such adhesively bonded structures tend to pull away from the tray thereby causing added inconvenience to both the dentist and the patient and frequently resulting in the necessity of taking additional impressions thereby prolonging the chair time of the patient.

Although various sets of adjustable and rigid dental impression trays have been provided heretofore, the principal differences between members in each set of trays have primarily been in the length or distal extent of the dental tray and in the entire relative size of each tray.

It has now been found that the principle variation in jaw sizes occur in the length of the dental arch and the lateral distance between corresponding teeth on opposite sides of the jaw. Accordingly, it is an object of the present invention to provide a new and improved low profile impression tray for accurately registering the dentition and only as much of the soft periodontal supporting structure as is needed to fabricate the desired corrective device.

Another object of the present invention is to provide a new and improved dental impression tray of the type described that includes means which facilitate planar release of the impression from the dentition thereby minimizing distortion and interference with marginal registration. Included in this object is the provision for an impression tray provided with a plurality of spaced handles facilitating the planar release of the impression from the dentition and reseating thereof in a facile manner without adversely affecting the impression.

A further object of the present invention is to provide a new and improved low profile impression tray of the type described having an interior grid-like surface effective to increase the surface area between the tray and the impression material to assure firm secure engagement therebetween.

Still another object of the present invention is to provide a low profile dental impression tray of the maxi]- lary type having means preventing overseating of the tray and the resultant spillage, waste of impression material and irritation to the patient.

A still further object of the present invention is to provide a disposable impression tray of the type described that is constructed of inexpensive plastic material easily trimmed by the dentist to accommodate only that portion of the dentition under treatment, such as merely the dentition itself when used for orthodontic models to which bands and appliances are to be applied. Included in this object is the provision for a tray made of material that can be readily sectionalized and adjusted to various minor anatomical configurations and is ideally suited to a transfer coping technique using rubber, plaster or combination withdrawals.

Other objects will be in part obvious and in part pointed out in more detail hereinafter.

These and related objects are accomplished in accordance with the present invention by providing a set of dental impression trays for both mixed and permanent dentition wherein the members of the set differ primarily in the size of the dental arch and lateral distance between corresponding molar positions on opposite sides of the jaw and the inclusion of a rise in the retromolar and tuberosity areas in the permanent dentition trays. Each tray in the set is a rigid low profile member comprised of a narrow substantially planar U-shaped base, lingual and labial walls integral with the base and upstanding from opposite edges thereof to provide a generally U-shaped cross section, an anterior handle projecting outwardly from the base and the labial wall and lateral tabs on opposite sides of the anterior handle extending laterally outwardly from the base at an acute angle thereto, said lateral tabs being located at the molar region on opposite sides of the tray.

A better understanding of the invention will be obtained from the following detailed description and the accompanying drawing which set forth an illustrative embodiment indicative of the way in which the principles of the invention are employed.

A BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective view of an empty impression tray of the mandibular type for use on permanent lower dentition;

FIG. 2 is a side view of the impression tray of FIG. 1 that has been oriented for positioning within a patients mouth to register the lower dentition;

FIG. 3 is a plan view of a mixed dentition tray of the mandibular type with phantom lines outlining the relative sizes of the three permanent dentition trays in the same set;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 1;

FIG. 5 is a sectional view taken along the line 5-5 of FIG. 2;

FIG. 6 is a fragmentary side view of the mixed dentition tray of FIG. 3 with a phantom line illustrating the relative size of the molar area of the tray of FIG. 2.

FIG. 7 is a plan view of the exterior of a dental impression tray of the maxillary type for use with the upper dentition and incorporating the features of the present invention;

FIG. 8 is a side view, partially broken away, of the tray of FIG. 7 oriented for positioning in the patients mouth to register the upper dentition; and

FIG. 9 is a sectional view taken along the line 99 of FIG. 8.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing in greater detail wherein like reference numerals indicate like parts throughout the several figures, a mandibular or lower dentition tray 10 for permanent teeth is shown as generally consisting of a U-shaped trough 12 for holding the impression material and a plurality of traymanipulating handles 14 and 16. The particular tray 10 illustrated is of medium size; however, as will be appreciated from FIG. 3, a set of mandibular trays conveniently consists of a mixed dentition tray 18 and small, medium and large permanent dentition trays 20, 10 and 22 respectively. These trays are very similar in construction and therefore will be described primarily with respect to the medium size mandibular tray 10. It will also be appreciated that each corresponding size of a maxillary tray in a set will be substantially identical in relative size except for the usual difference between these two types of trays. Accordingly, for ease of understanding and simplicity of illustration only the preferred embodiment of a medium permanent tray 10 will be described in detail. As will be appreciated, this embodiment of the tray including the specific dimensions thereof are provided by way of illustration only and are not intended to be a limit on the practice of the invention.

Referring now specifically to FIGS. 1-5 the dental impression tray indicated generally by the numeral 10 includes the trough 12 comprised of a narrow, generally planar base or floor portion 26 of U-shaped configuration having a labial or outer wall portion 28 and a lingual or inner wall portion 30 integrally upstanding from opposite edges of the floor portion 26 in a continuous fashion along its entire arcuate extent. As best shown in FIGS. 1, 4, and 5, the base 26 and integral labial and lingual wall portions 28 and 30 collectively impart a generally U-shaped cross sectional configuration to the tray resulting in its troughlike appearance. The wall portions extend outwardly from the base in relative diverging fashion and are of a dimension sufficient to enclose the usual height of a clinical crown as well as the lingual, crestal and gingival attachments thereto. However, the wall portions do not extend excessively beyond these attachment areas and unlike trays utilized heretofore only exhibit a height which exceeds the exposed tooth length by a distance equal to or less than one-half that length.

Advantageously, one of the unique features of the present invention is the consistently narrow dimension of the base or floor portion 26 in all trays within each set. In fact, these base or floor portions are substantially identical in the small, medium and large permanent dentition members of the set as well as in the mixed dentition tray. As mentioned hereinbefore, the

base or floor portion 26 is substantially planar and of generally U-shaped configuration; however, as best shown in FIG. 2, it exhibits a slight concave curvature from front to back, commonly referred to as the Curve of Spee. The slight arcuate configuration extends from the central portion of the tray rearwardly toward the second molar area. Distally beyond that point the floor exhibits a substantially increased curvature referred to as the retromolar rise. That area, designated by the numeral 31, is slightly exaggerated in FIGS. 2 and 6 for illustrative purposes.

The breadth of base portion 26 increases slightly from the central portion of the tray toward the retromolar rise .31 and in the preferred embodiment exhibits dimensions of approximately mm at the central area with a gradual increase in about 12 mm at the bicuspid area and 16 mm at the second molar area of each tray. As mentioned, it is an advantageous feature of the present invention that the foregoing dimensions remain substantially constant for the small, medium and large permanent dentition trays and preferably are also utilized in the mixed dentition tray of each set. In this way the amount of impression material that must be used may be held to a minimum while at the same time fully and completely accommodating all of the teeth regardless of the size of the tray that need be used.

As mentioned, another feature of the present invention is the low profile labial and lingual walls of the tray. As shown in FIGS. 1 and 2, the labial or outer wall portion 28 is integrally joined to the base portion along one edge thereof and depends therefrom along the entire extent of the U-shaped base portion. The distance of the free edge 32 of the labial or outer wall portion 28 from the base portion 26 varies along its length in order to accommodate certain muscle and soft tissue areas. For example, at the central portion of the tray the free edge of the labial wall portion is provided with a recess or cleft 34 to accommodate the labial frena. Accordingly, the dimension of the wall portion at the frenum area is only about 12 mm as compared to a conventional lower anterior central tooth length of about 8-11 mm. The free edge 32 gradually undulates as it sweeps rearwardly, the undulation providing a muscle relief portion 36 in the bicuspid area having a height of about 12 mm bounded by crests 40, 42 on opposite sides thereof having wall dimensions of about 14 mm and 16 mm, respectively. As seen in FIGS. 1 and 2, the labial wall falls off sharply in the retromolar area 31 to a dimension of only about 9mm immediately prior to joining the base or floor portion 26.

The labial wall portion 28 not only varies in depth but also in angular disposition relative to the base portion 26 as the wall extends rearwardly. For example, the labial wall at the cleft 34 is disposed at an angle of 90 degrees to the base or floor portion 26 and maintains this relationship across the full anterior extent of the tray. However, in the cuspid area the wall portion 28 starts to flare slightly labially so that it is disposed at an angle of 105 degrees to the base portion 26 as the wall reaches the second bicuspid area of the tray.

The lingual or inner wall portion 30, on the other hand, is disposed at an angle of about 120 degrees to the base 26 at the midline of the tray and is of a substantially constant dimension in the central area, i.e. about 12 mm, until it reaches the biscuspid area where it initiates a gradual increase to a dimension of about 16 mm in the molar area and adjusts to an angle of about 105 degrees. This low profile angular relationship of the walls to the base also substantially limits the amount of impression material required by the tray of the present invention.

which provides for a clean unobstructed withdrawal for a true unaltered registration of the dentition.

As mentioned, it is a feature of the present invention that the floor portion in each member of the dental tray As best shown in FIG. 1, the interior of the trough 12 5 set remains substantially unchanged but that each defined by the base and wall portions is provided with member varies from other members of the set primarily a scored, serrated or grid-like roughened surface conby the lateral distance between corresponding teeth figuration. This permits greater surface area contact and by the length of the dental arch. Accordingly, as between the interior of the tray and the impression mashown in FIG. 3 the mixed small, medium and large terial carried therein thereby obviating the difficulties l0 trays of the set vary in the dental arch and in the lateral formerly encountered when the impression material dimension between corresponding molars. The particureadily separated from the tray. At the same time this lar arch form can easily be obtained by three measureis accomplished without the necessity for apertures and merits, namely the lateral distance between correis particularly effective when adhesive is applied to the sponding molars, such as the first molar line 48 of tray interior of the tray so as to secure the impression mate- 15 18 and the second molar line 50 of tray 20 shown in rial therein. FIG. 3, the center line distance 52 or 54 between the One of the particularly unique features of the present laterally extending lines 48 or 50 and the center of the invention is the provision for a plurality of spaced tray tray floor at the center line and the peripheral dimenmanipulating handles. In the preferred embodiment sion of the tray between corresponding molars on opthree such handles are provided, a central or anterior 20 posite sides of the tray. In accordance with the present handle 14 and a pair of lateral handles 16 on opposite invention, it has been found that only three trays are sides of the anterior handle 14. All three handles eX- required to accommodate a wide variety of jaw forms tend outwardly from the labial or outer wall 28 at its where permanent teeth are involved and only a single point of juncture with the base or floor portion 26. A tray is required for jaws of mixed dentition. Thus a set though these handles or tabs can be of identical length, of only four trays will readily accommodate substanpreferably the anterior handle 14 is slightly larger than tially all jaw configurations for patients of about seven the lateral handles 16 by a ut 3-7 mm- Th th ha years of age and older. Typical measurements for these dles positively locate three points of the plane of withfour trays of both the maxillary and mandibular type drawal of the tray and are of substantial assistance in are set forth in Table I;

Table I Maxillary Mandibular Tray Lateral Center Periphery Lateral Center Periphery Mixed 1.63" 1.00" 4.38" 1.63" 0.87" 4.25"

Small 2.00" 1.38" 5.00" 1.86" 1.25" 4.75"

dium

Large 2.25" 1.75" 5.75" 2.13" 1.50" 5.25"

holding the tray level as it is lifted from the dentition. As will be appreciated, the mixed dentition tray does This is particularly important since the lateral handles not include a retromolar rise and the lateral measurepermit a withdrawal force at the distal portion of the ment between corresponding teeth on opposite sides of impression simultaneously with a withdrawal force apthe jaws are generally taken across the first molar locaplied at the anterior portion of the tray. The tray thus tion rather than the second molar location. Additioncan be lifted straight up without subjecting the tray to ally, since it does not have a retromolar rise portion, the angular forces that are required when only a single the mixed dentition tray 18 exhibits a slightly different anterior handle is used to effect withdrawal of the imconfiguration from the remaining trays in the set. This pression from the dentition. In the specific embodiment difference in configuration is best illustrated in FIG. 6 used for illustrative purposes and as best shown in where the molar area of the mixed dentition tray is FIGS. 2, 4 and 5, the anterior handle 14 is of greater shown in relationship to the medium size tray 10 of length than the lateral handles 16 and may, for exam- FIG. 2. ple, be of a length of about 16 mm while the lateral handles'exhibit a length o only about? o Referring now to the maxillary tray illustrated in Addiuonany, the antenor handle 14 d'sposed at an FIGS. 7-9, the tray construction is similar to that disangle of about degrees to the lablal or outer wall cussed in connection with the mandibular trays. How- 28 and at an angle of about 150 degrees to the base or ever, as is apparent from FIG 8 the generally planar floor portion 26 of the tray. On the other hand, the latushaped base or floor portion 62 of the maxillary tray era] handles or tabs 16 are dlsposed at an angle of 60 60 exhibits a slight convex curvature corresponding to about 120 degrees to the labial side wall 28 and at an the Curve of Spee and complgmemary to the base pop angle of about degrees to the floor porno 26 of tion 26 on the mandibular tray. The lingual wall portion the tray. The anterior handle 14 is also contoured so 64 is provided with a palatal Stop that takes the form that it can easily accommodate the dentists thumbs of flanges 66 on the top free surface of the lingual wall during removal of the tray. In operation, after the im- 65 at the molar area AS Shown, the fl 66 Starts at a pression material has set on the dentition, the dentist need merely contact the underside of the anterior handle 14 with his thumbs and the underside of the lateral handles with his index fingers and lift the tray away from the dentition by a smooth, upward movement point distal to the first bicuspid and extends rearwardly to the second molar area. The flanges are not of substantial breadth, exhibiting a width of only about 5 mm and are disposed at an angle of about 135 degrees to the lingual wall 64. As can be apapreciated the inwardly extending flanges 66 prevent overseating of the low profile and prevent possible irritation to the patient accomapnying such overseating.

In a mannner complementary to the mandibular tray, the maxillary tray includes a tuberosity rise 68 on the free or terminal ends thereof and, as shown in FIG. 8, also includes a grid-like or serrated inner surface 70 to provide improved retention of the impression material within the tray. The labial wall portion 72 is angularly disposed relative to the floor portion 62 at substantially the same angle as the corresponding wall 28 of the mandibular tray while the lingual wall 64 preferably is disposed at a constant 120 degree angle to floor portion 62 throughout the length of wall 64. Additionally, the labial wall portion 72 exhibits substantially the same undulating configurations as wall portion 28 to provide relief for the frenum and muscle areas in the upper jaw.

Although the anterior and laterial handles 74, 76, respectively of the maxillary tray 60 can be of a size and angulr relationship substantially identical to the three tabs on the mandibular tray, it is generally preferred that the anterior handle 74 of the maxillary tray extend at an angle of about 105 degrees relative to the labial wall portion 72 rather than the 120 degrees orientation exhibited by the handle 14 and that the lateral tabs or handles 76 extend labially at an angle of 120 degrees to the base or floor portion 62 rather than the 135 degree orientation of the tabs 16 of the mandibular tray. Additionally, the lateral tabs or handles 76 on the maxillary tray are slightly shorter, extending for a distance of about only 6 mm rather than the 9 mm length preferred for tabs 16. As will be appreciated, a set of maxillary trays will correspond in number and size to the set of mandibular trays discussed hereinbefore.

Although the trays in each set may be made from a variety of different materials, it is generally preferred that rigid, low-cost plastic be employed. The particular type of plastic is not critical although it should exhibit the dimensional stability or rigidity necessary to provide the desired result. In addition to low cost, the plastic should facilitate easy sectionalization and trimming of the wall portions to accomodate the individual patient. For assisting in sectionalization each tray is provided with score lines, such as the lines 80 on the exterior tray 10 at the locations of each tab or handle. As shown, the score lines 80 preferably bisect each handle or tab so that tab portions remain functional even though only a section of the tray is utilized. For example, if an impression is required for only the anterior dentition, the tray can be broken on the score lines located at each lateral handle 16 and the advantageous three point manipulation of the tray is retained.

Thus, as can be seen by the foregoing detailed description, the present invention provides a new and improved dental impression tray which includes three tabs or handles for even, plane-like withdrawal of the impression from the dentition. The handles are short strong angulated members designed so as not to interfere with the sides of the mouth or with the placement and removal of the impressions. Additionally, the trays provide a retromolar rise and tuberosity rise within the distal molar area and the maxillary tray provides an angulated flange stop to prevent overseating and resultant irritation. The labial and lingual walls of the tray are of low profile to minimize the amount of impression material required while at the same time provide relief for frenum and muscle attachments. As will be appreciated, the trays are preferably made from material that can be readily cut away in order to easily adjust the side walls to accommodate the particular patient. Further, a gridlike interior surface is provided on the trays to improve retention of the impression material and is particularly effective in combination with adhesive coatings. The tray is of simple yet sturdy design and can be made from inexpensive plastic material so as to facilitate its use and disposal. The set of trays employ a floor or base portion which is substantially uniform throughout each member of the set with each member varying from other members principally by the lateral distance between corresponding teeth and by the size of the dental arch.

As will be appreciated by persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

I claim:

1. A rigid disposable low profile dental impression tray for accurately registering a dentition for crown and bridgework comprised of a narrow U-shaped substantially planar base of dental arch configuration conforming in the posterior and lateral curvatures to the occlusal surfaces of the dentition and inner and outer walls integral with the base and upstanding from opposite edges thereof to provide a trough of generally U- shaped cross section, an anterior handle integrally projecting outwardly from the base at an obtuse angle to both the base and the outer wall and lateral tabs spaced on opposite sides of the anterior handle extending laterally outwardly from the base at a more acute angle than said anterior handle, said lateral tabs being located at about the bicuspid/molar area on opposite sides of the tray, said anterior handle being broader than the lateral tabs, said anterior handle and lateral tabs facilitating simultaneous substantially planar engagement thereof parallel to the occlusal masticatory surfaces of the dentition for vertical withdrawal of the tray from said surfaces, said inner and outer walls extending from the base sufficiently only to accurately register the dentition and the immediately adjacent periodontal supporting tissue.

2. The dental impression tray of claim 1 wherein the outer wall extends integrally from the base for a height that encompasses the soft supporting tissue by a distance up to at least one half the length of the exposed teeth in confronting relationship therewith.

3. The dental impression tray of claim 1 adapted for use as a maxillary tray wherein the inner wall includes a lingually projecting flange extending rearwardly from about the first bicuspid area toward the second molar area, said flange providing a palatal stop for the tray.

4. The dental impression tray of claim 1 wherein the anterior handle is sufficiently larger than the lateral tabs to facilitate engagement by two thumbs of the operator during vertical withdrawal of the tray.

5. A set of dental impression trays as set forth in claim 1 wherein each member of the set differs from other members thereof by both the length of the dental arch and the transverse dimension between corresponding teeth on opposite sides thereof.

6. The set of dental impression trays of claim 5 including a mixed dentition tray and a plurality of permanent dentition trays wherein the mixed dentition tray terminates at the second molar area and the permanent dentition trays exhibit a molar rise extending distally from the second molar area.

7. The set of dental impression trays of claim wherein the transverse dimension of the base of each member of the set is substantially identical at corresponding locations.

8. The set of dental impression trays of claim 5 of the maxillary type comprised of a mixed dentition tray and small, medium and large dentition trays wherein the trays exhibit substantially the dimensions set forth in the following table with the dimension for the mixed tray being taken at the first molar area and the dimensions for the permanent trays being taken at the second molar area:

9. The set of dental impression trays of claim 5 of the mandibular type comprised of a mixed dentition tray and small, medium and large dentition trays wherein the trays exhibit substantially the dimensions set forth in the following table with the dimension for the mixed tray being taken at the first molar area and the dimensions for the permanent trays being taken at the second molar area:

10. The set of dental impression trays of claim 9 wherein the mixed dentition tray terminates at the second molar area and the permanent dentition trays include a molar rise distally of the second molar area.

11. The set of dental impression trays of claim 5 of the maxillary type wherein the interior walls of each tray are provided with a lingually projecting flange extending rearwardly from about the first bicuspid area toward the second molar area, said flange providing a palatal stop for the tray.

12. The set of dental impression trays of claim 5 wherein the trays are constructed of dimensionally stable plastic material. 

1. A rigid disposable low profile dental impression tray for accurately registering a dentition for crown and bridgework comprised of a narrow U-shaped substantially planar base of dental arch configuration conforming in the posterior and lateral curvatures to the occlusal surfaces of the dentition and inner and outer walls integral with the base and upstanding from opposite edges thereof to provide a trough of generally U-shaped cross section, an anterior handle integrally projecting outwardly from the base at an obtuse angle to both the base and the outer wall and lateral tabs spaced on opposite sides of the anterior handle extending laterally outwardly from the base at a more acute angle than said anterior handle, said lateral tabs being located at about the bicuspid/molar area on opposite sides of the tray, said anterior handle being broader than the lateral tabs, said anterior handle and lateral tabs facilitating simultaneous substantially planar engagement thereof parallel to the occlusal masticatory surfaces of the dentition for vertical withdrawal of the tray from said surfaces, said inner and outer walls extending from the base sufficiently only to accurately register the dentition and the immediately adjacent periodontal supporting tissue.
 1. A rigid disposable low profile dental impression tray for accurately registering a dentition for crown and bridgework comprised of a narrow U-shaped substantially planar base of dental arch configuration conforming in the posterior and lateral curvatures to the occlusal surfaces of the dentition and inner and outer walls integral with the base and upstanding from opposite edges thereof to provide a trough of generally U-shaped cross section, an anterior handle integrally projecting outwardly from the base at an obtuse angle to both the base and the outer wall and lateral tabs spaced on opposite sides of the anterior handle extending laterally outwardly from the base at a more acute angle than said anterior handle, said lateral tabs being located at about the bicuspid/molar area on opposite sides of the tray, said anterior handle being broader than the lateral tabs, said anterior handle and lateral tabs facilitating simultaneous substantially planar engagement thereof parallel to the occlusal masticatory surfaces of the dentition for vertical withdrawal of the tray from said surfaces, said inner and outer walls extending from the base sufficiently only to accurately register the dentition and the immediately adjacent periodontal supporting tissue.
 2. The dental impression tray of claim 1 wherein the outer wall extends integrally from the base for a height that encompasses the soft supporting tissue by a distance up to at least one half the length of the exposed teeth in confronting relationship therewith.
 3. The Dental impression tray of claim 1 adapted for use as a maxillary tray wherein the inner wall includes a lingually projecting flange extending rearwardly from about the first bicuspid area toward the second molar area, said flange providing a palatal stop for the tray.
 4. The dental impression tray of claim 1 wherein the anterior handle is sufficiently larger than the lateral tabs to facilitate engagement by two thumbs of the operator during vertical withdrawal of the tray.
 5. A set of dental impression trays as set forth in claim 1 wherein each member of the set differs from other members thereof by both the length of the dental arch and the transverse dimension between corresponding teeth on opposite sides thereof.
 6. The set of dental impression trays of claim 5 including a mixed dentition tray and a plurality of permanent dentition trays wherein the mixed dentition tray terminates at the second molar area and the permanent dentition trays exhibit a molar rise extending distally from the second molar area.
 7. The set of dental impression trays of claim 5 wherein the transverse dimension of the base of each member of the set is substantially identical at corresponding locations.
 8. The set of dental impression trays of claim 5 of the maxillary type comprised of a mixed dentition tray and small, medium and large dentition trays wherein the trays exhibit substantially the dimensions set forth in the following table with the dimension for the mixed tray being taken at the first molar area and the dimensions for the permanent trays being taken at the second molar area:
 9. The set of dental impression trays of claim 5 of the mandibular type comprised of a mixed dentition tray and small, medium and large dentition trays wherein the trays exhibit substantially the dimensions set forth in the following table with the dimension for the mixed tray being taken at the first molar area and the dimensions for the permanent trays being taken at the second molar area:
 10. The set of dental impression trays of claim 9 wherein the mixed dentition tray terminates at the second molar area and the permanent dentition trays include a molar rise distally of the second molar area.
 11. The set of dental impression trays of claim 5 of the maxillary type wherein the interior walls of each tray are provided with a lingually projecting flange extending rearwardly from about the first bicuspid area toward the second molar area, said flange providing a palatal stop for the tray. 